1. Field of the Invention
This invention relates to the field of medical products. More specifically, the invention comprises a modular system for applying cryotherapy to a patient's shoulder.
2. Description of the Related Art
It is now widely recognized that the application and maintenance of “cold therapy” in the hours and days following surgery significantly improves patient outcomes. The terms “cold therapy” and “cryo therapy” are often used interchangeably. The present application will use the term “cryo therapy.”
Ice packs are often used for cryo therapy. These are placed on the affected shoulder and held in position using compressive wraps or other known techniques. “Gel packs” may be substituted for the ice packs in some applications. Another less common approach is the use of cooled fluid (often water) circulated through a sealed bladder which is placed in contact with the affected area.
The use of ice packs has several known disadvantages. One disadvantage is that the patient's skin must be separated from the ice pack by a layer of appropriately insulating material. This is often required to prevent frost burns. Since the ice pack will remain at 0 degrees Celsius while the phase change from solid to liquid is progressing, it is capable of cooling the patient's skin to a harmful extent. Thus, it is often necessary to use an insulating layer which provides some (but not too much) insulation.
Gel packs alleviate some of the frost burn concern since they generally do not undergo a phase change. The gel pack remains liquid at the temperatures found in most freezers. Thus, when placed on the patient, a gel pack warms up to a more acceptable temperature (well above) degrees Celsius) in a relatively short period of time). Of course, lacking a phase change, the gel pack cannot absorb as much heat as a conventional ice pack.
In addition, both the conventional ice packs and the gel packs are difficult to remove and replace. Such packs must be frequently exchanged for fresh ones in order to make the cryo therapy effective. One set of packs is typically applied to the patient while one or more other sets of packs are cooling in a nearby freezer. The packs on the patient must be exchanged for new ones once they reach an ineffective temperature (typically about 10 degrees Celsius). This process is difficult in the prior art because the compressive wrap used to hold the packs in place must be unwound and then reapplied.
The use of a cooled circulating fluid avoids the frost burn problems present with ice packs and—to a lesser extent—gel packs. However, the bladder in such a system must be connected to a large and bulky cooling unit by an input and output line. This restricts patient mobility. The cooling unit also tends to be noisy, which can disturb patient sleep patterns.
The present invention seeks to eliminate or reduce the problems present in the prior art. It uses replaceable packs containing a suitable cooling mediaum. The preferred cooling medium is one that freezes between about 5 degrees Celsius and about 20 degrees Celsius. Such a medium can absorb considerable heat via the phase change from a solid to a liquid. In addition, such a cooling medium poses little risk of tissue damage (as it will remain at its melting temperature until all the medium has transitioned from a solid to a liquid).
The solid phase of the cooling medium is also significant. It is obviously undesirable for a bag of liquid cooling medium to freeze into a solid block. It is preferable to have the phase change transition into a highly structured crystalline form akin to snow. The bag of frozen cooling medium will then be soft and malleable.
The present invention provides a modular shoulder cooling system using bags of frozen cooling medium. The system facilitates easy exchange of the bags so that the bags can be replaced once their ability to absorb heat is diminished.